A Cassegrain antenna consists of three parts, namely, a main reflector, a sub-reflector, and a radiation source. The main reflector is a rotating paraboloid reflector, and the sub-reflector is a rotating hyperboloid reflector. In structure, one focus of a hyperboloid coincides with that of a paraboloid, and the focal axis of the hyperboloid coincides with that of the paraboloid, and a radiation source is located on the other focus of the hyperboloid. The sub-reflector reflects an electromagnetic wave, radiated by the radiation source, to the main reflector, and then the main reflector reflects back the electromagnetic wave to obtain a plane wave beam of a corresponding direction, so as to implement directional transmission.
It can be seen that, a main reflector of a conventional Cassegrain antenna needs to be processed to a highly precise paraboloid. However, such processing to a highly precise paraboloid features great difficulty and relatively high costs.